Cold-rolled stainless steel strips are generally subjected to annealing heat treatment for the purpose of changing work-hardened layers. Oxide scales occurring on the surface of stainless steel during this treatment cause significant deterioration in its value as a commercial product. Such oxide scales therefore must be removed. Descaling methods concern a process in which stainless steel is electrolyzed in a strong acid such as sulfuric acid and a method in which stainless steel is immersed in a molten alkaline salt. These methods involve problems with respect to the roughness of the surface, a lengthy period of time for the descaling process, and difficulty in handling. In order to resolve the problems, there has been proposed a method in which stainless steel is electrolyzed in an aqueous neutral salt solution and then immersed in an aqueous solution of a mixture containing nitric acid and fluoric acid, as disclosed in Japanese Patent Examined Publication No. 38-12162. Also, a method in which stainless steel is electrolyzed in an aqueous neutral salt solution and then electrolyzed in a solution containing nitric acid ions, has been disclosed in Japanese Patent Examined Publication No. 53-13173.
In the above-mentioned prior art, attention is paid only to descaling of the surface of the stainless steel, and insufficient consideration is given to the glossiness and the smoothness of the surface of the descaled stainless steel or to the speed of descaling treatment and improvements of a high-temperature operation when effecting immersion in a molten alkaline salt. There are therefore difficult problems with respect to an increase in the speed of descaling and an improvement in the workability.